In the processing of many fabrics, particularly knitted fabrics in either tubular or flat form, many of the significant commercial finishing techniques involve the application of lengthwise mechanical compressive shrinkage to the fabric by processes which may be regarded as asy metrical, in that one side of the fabric is acted upon at least somewhat differently than the other side. By way of example, one of the important commercial processes for the compressive shrinkage of tubular knitted fabric, the "Compax" process, involves directing the fabric into a compacting zone formed in part by feeding and retarding rollers rotating at slightly different speeds. The fabric is being introduced into the zone at the speed of the feeding roll and is being decelerated in the treating zone to the speed of the retarding roll. As the fabric passes between these two rollers, it is being acted upon simultaneously by rollers moving at different surface speeds, so that at least one of the rollers is moving relative to the fabric. One surface of the fabric thus may become slightly "burnished", so that it may appear slightly more shiny than the opposite surface. This is referred to as "two sidedness".
Typically, two sidedness resulting from asymmetrical compressive shrinkage treatment, sometimes herein called burnish compacting is more pronounced with colored fabrics, and of course may be more troublesome in connection with fabrics processed in tubular form, where one side of the fabric tube constitutes the same "surface" as the other side of the tube (e.g., both the top and the bottom surfaces of a fabric tube may constitute the outside surface of a garment).
In some cases, asymmetrical processing of the fabric is at least partially compensated by treatment of the fabric in two stages, such that any burnishing action is applied to one surface in the first stage and to the opposite surface in the second stage. By appropriately proportioning the amount of compressive shrinkage effort applied at the respective stations, it may be possible to substantially balance the surface appearance of the fabric. Nevertheless, even using a two station machine, some two sidedness may result, either because it is not practical to balance it out altogether, or because the desired proportioning of effort in order to achieve balance of appearance may not be consistent with optimum balance of effort for achieving the desired total compressive shrinkage effort. Moreover, in some cases the fabric itself (e.g., ribbed fabrics) may be of a nature such that its appearance can be changed undesirably during compressive shrinkage treatment, as by reason of the thickness compression of the fabric, as well as any burnishing action.
In accordance with the invention, two sidedness and other undesired effects in mechanically compressively shrunk fabric may be greatly improved by a new moisturizing treatment, in which significant amounts of moisture are imparted with great uniformity of distribution to the opposite surfaces of the fabric, following compressive shrinkage treatment, after which the fabric is immediately directed into a Palmer-type dryer, in which the fabric is held in a geometrically stabilized condition against the heated surface of a dryer drum, by means of a porous conveyor blanket. Upon emergence from the discharge end of the Palmer-type dryer, the fabric is in a finished condition, with significantly improved surface appearance, both from the standpoint of two sidedness and/or thickness compression (as in the case of a ribbed fabric).
In accordance with the invention, moisture is applied to the opposite sides or surfaces of the fabric in an extremely finely divided spray mist or fog, under conditions that reliably avoid the formation of droplets, which might spot or mark the fabric. The amount of moisture to be applied to the surface of the fabric is somewhat empirical for different fabrics, but in any event is greater than that which could possibly be achieved by either steaming of the fabric or by natural moisture regain. In this respect, steaming of the fabric may add approximately two percent or so moisture by weight, whereas natural moisture regain with time may add about six percent. In contrast, in some cases, with light fabrics subjected to substantial compressive shrinkage treatment, it might be appropriate in the process of the invention to add surface moisture constituting up to fifty percent by weight of the fabric.
Pursuant to one aspect of the invention, the rate of moisture application to the fabric, for a given speed of travel of the fabric, is set such that the fabric will have been adequately dried by the time it emerges from the Palmer-type dryer. The spray mist application is set to be applied at a constant rate, and the amount applied to the fabric therefore will vary as a function of the speed of travel of the fabric through the misting zone. An operator of the process observes the fabric emerging from the Palmer-type dryer, and the process can be progressively speeded up until the emerging fabric evidences undesirable two sidedness, after which the processing speed may be slowed down slightly, so that a greater amount of moisture is applied to the fabric as it travels to the misting zone. Experience with the process indicates that restoration of the desired surface appearance of the fabric is to a great extent a function of the amount of moisture applied to the surface of the fabric, such that, once a constant rate of spray application has been established, excellent control over the process may be achieved by simply controlling the speed of travel of the fabric through the spraying-drying sequence. The spraying and the drying at all times remain in balance, because whenever the fabric speed is reduced to enable more moisture to be applied, its speed of passage through the dryer is correspondingly reduced, and vice versa, so that the drying effort is at all times consistent with the amount of moisture application.
In accordance with other aspects of the invention, an improved apparatus arrangement is provided for the uniform application of spray mist to the opposite surfaces of a moving fabric web, so that highly controlled amounts of moisture may be applied to opposite sides of the fabric, with consistent reliability, free of condensation spots or the like. It will be understood, of course, that the opposite "sides" of a tubular fabric will be the same surface. Thus, wherever reference is made herein to opposite sides or opposite surfaces of a fabric, such reference will be understood to mean the outside surface of a tubular fabric or the two surfaces of an open width fabric, as the case may be.
Pursuant to the invention, the fabric is conveyed in a completely tension free manner between opposed banks of spray nozzles, directed at the respective opposite surfaces of the fabric. Each bank of nozzles consists of a series of relatively closely spaced fine-atomizing spray nozzles extending across the full width of the fabric and arranged to discharge an air-atomized fine mist of moisture on the fabric surface. To accommodate the inevitable starting and stopping of the process from time to time during otherwise continuous production runs, means are provided for muffling the spray discharge of the nozzles during stoppage of the processing line, so that the nozzles do not have to be turned off. In this respect, stopping and starting of the air-atomizing nozzles may be occasioned by momentary sputtering and discharge of larger-than-desired droplets of moisture, which could otherwise spot the fabric.
For a more complete understanding of the above and other features and advantages of the invention, reference should be made to the following detailed description of a preferred embodiment and to the accompanying drawings.